The present invention relates generally to a tire pressure monitoring system, and more particularly, to a method for providing variable power output of a low frequency initiator to allow flexibility in the packaging thereof.
Various types of pressure sensing systems for monitoring the pressure within the tires of an automotive vehicle have been proposed. Such systems generate a pressure signal using an electromagnetic (EM) signal, which is transmitted to a receiver. The pressure signal corresponds to the pressure within the tire. When the tire pressure drops below a predetermined pressure, an indicator is used to signal the vehicle operator of the low pressure.
Various tire manufacturers have suggested various locations for the pressure sensors. Known systems include coupling a pressure sensor to the valve stem of the tire. Other known systems and proposed systems locate the pressure sensors in various locations within the tire wall or tread. Tires are mounted to wheels that are commonly made from steel or aluminum.
In addition, it is desired to have a system that automatically determines the locations of the tire pressure sensors relative to the vehicle. Known location systems require the vehicle operator to place a magnet in the vicinity of the tires. However, such systems rely upon the vehicle operator performing the programming in a predetermined order. Thus, such systems are subject to errors.
It would therefore be desirable to provide flexibility for automatically determining the positions while allowing the components of such a system to be placed at different locations for different types of vehicles.
The present invention provides a system and method for automatically identifying the position of the tires relative to the vehicle. The present invention is directed to a system that uses a low frequency initiator to initiate a response from a pressure sensor to automatically determine the position of each of the pressure sensors within the system.
In one aspect of the invention, a tire pressure monitoring system has a plurality of initiators that are fixedly attached to the vehicle at a respective plurality of locations. A plurality of tires having a respective plurality of transmitters generates a respective plurality of transmitter identification signals. A controller is coupled to the plurality of initiators. The controller activates the plurality of initiators by generating a respective plurality of initiator signals from the plurality of initiators. The plurality of initiator signals have a first power level. The controller increases the first power level incrementally to a final power level until said controller receives a sensor signal from each of the plurality of tire transmitters.
In a further aspect of the invention, a method of operating a tire pressure monitoring system for a vehicle having a plurality of tire locations comprises activating a first initiator by generating a first initiator signal from a first initiator at a first of the plurality of tire locations, said first initiator signal having a first power level, and increasing the first power level incrementally to a final power level until receiving a first sensor signal from a first sensor.
One advantage of the invention is that the position of the low frequency initiator may be changed to various locations in various vehicle lines. The low frequency initiator may be positioned in various locations within the wheel well or on the body of the vehicle adjacent to the wheel well depending on the various configurations and packaging requirements by the various types of vehicles. Another advantage of the invention is that by providing only just enough power at the low frequency initiator to generate a response from the tire pressure transmitter, the likelihood of receiving a response from an adjacent vehicle is thus minimized.
One advantage of the invention is that no operator intervention is required for the identification, which in one embodiment, may be performed every time the vehicle is running and the speed exceeds a predetermined speed such as 20 miles an hour. This prevents the vehicle operator from inadvertently forgetting to reset the system.
Other advantages and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.